1. Field of the Invention
The field of art to which this invention relates is surgical instruments, in particular, electrosurgical cutting instruments.
2. Description of the Related Art
Surgical instruments which mechanically cut tissue are well known in the surgical arts. A surgical scissor for use in open surgical procedures is illustrated in FIG. 1 and referred to generally by reference numeral 10. The scissor has two opposing blades 12,14, each with a cutting edge 16,18. The blades pivot about a pin, rivet, or screw 20. The scissors 10 further having first and second elongated members 22,24, each member having a proximal end 26,28 and a distal end 30,32. Finger loops 34,36 are provided at the proximal ends 26,28 of the first and second elongated members 22,24. The blades 12,14 are disposed at the distal ends 30,32 of the elongated members.
Referring now to FIG. 2, the blades 12,14 are shown cutting a piece of tissue 38. As can be seen, the cutting edges 16,18, when closed upon the tissue 38, at a time just prior to cutting, causes a region of tissue 40 to tear, resulting in trauma to the tissue.
The cutting of tissue during a surgical procedure results in bleeding. Controlling bleeding during surgery accounts for a major portion of the time involved in surgery. In particular, bleeding that occurs when tissue is incised or severed can obscure the surgeon's vision, prolong the operation, and adversely effect the precision of cutting. Blood loss from surgical cutting may require blood infusion, thereby increasing the risk of harm to the patient.
Electrosurgical instruments have been developed for reducing bleeding by cauterizing tissue and coagulating blood. These instruments include both monopolar and bipolar devices in which radio frequency (RF) energy is used to provide the heat necessary for cauterization and coagulation. Monopolar devices are typically used in conjunction with a grounding pad wherein one pole of an electrosurgical generator is mounted to the instrument and one pole is mounted to the grounding pad. Electrical current travels from the instrument through the patient's body to the grounding pad. Bipolar instruments are typically connected to both poles of the electrosurgical generator. Current flow is typically limited to tissue adjacent to the working end of the bipolar instrument.
Furthermore, these instruments can be of a reusable type (the instrument is cleaned and disinfected or sterilized before each use) or a disposable type (disposed of after each use). Each of these types can be provided in different sizes, shapes, and configurations so as to be suitable for either endoscopic or open surgery.
In "open" surgical procedures, the surgeon gains access to work inside the body by cutting large incisions through the body wall, then stretching the overlying tissue apart to provide visibility and room to manipulate his hands and instruments. Because of the relatively large working area provided in open surgical procedures, the instruments used can be larger. They typically have conventional scissors handles with finger loops and a pivot point about which the handles pivot to actuate the working end.
In endoscopic surgical procedures, a trocar provides a puncture wound in the body wall. The trocar is removed leaving a hollow tube providing access to the body cavity. A miniature television camera is inserted through the trocar tube to provide a video image of the inside of the body cavity. Specially designed surgical instruments are then inserted through other small trocar tubes to perform the surgery. Surgical instruments of this type typically have a long tubular body designed to pass through the trocar tubes. The working end, connected to the distal end of the tubular body must likewise pass through the trocar tubes and are therefore typically small in cross section. Typically, a scissors-like actuating means or a pistol grip actuating means is disposed on the proximal end of the tubular body to remotely actuate the working end. The actuating means is typically connected to the working end by a mechanical linkage.
More recently, electrosurgical cutting devices have been developed which combine mechanical cutting with electrosurgical cauterization and cutting. Examples of these devices include electrosurgical scissors.
U.S. Pat. No. 5,330,471 discloses bipolar electrosurgical scissors having electrically insulated cutting edges. The cutting edges provide for simultaneous hemostasis and mechanical cutting of tissue. U.S. Pat. No. 5,352,222 discloses bipolar electrosurgical scissors. The scissors have blade supports with blades mounted thereto and separated by a layer of insulation. U.S. Pat. No. 4,248,231 discloses an electrosurgical scalpel wherein an instrument is disclosed having an insulated blade and electrode mounted thereto.
Although the electrosurgical cutting devices of the prior art are useful and effective, there are several deficiencies associated with their use. In particular, as the scissor blades rotate in a scissors-like manner, the mechanical cutting of tissue occurs in a limited area at a point immediately adjacent to the closure point of the cutting edges. Additional disadvantages of conventional electrosurgical scissors include:
a. They are not very useful for large cutting and dissecting; PA1 b. The scissor-like motion which requires a sliding point of contact between blades causes the blades to wear, increasing the trauma to the cut tissue caused by the dull blades; and PA1 c. Scissor-like instruments are very difficult to manufacture, requiring complex surface contours, strict dimensional tolerances, and precise blade adjustment.
Accordingly, there is a need in the art for an improved electrosurgical cutting instrument which is capable of simultaneous cutting and cauterization of a linear section of tissue.